Many disease states are characterized by differences in the expression levels of various genes either through changes in the copy number of the genetic DNA or through changes in levels of transcription of particular genes (e.g., through control of initiation, provision of RNA precursors, RNA processing, etc.). For example, losses and gains of genetic material play an important role in malignant transformation and progression. These gains and losses are thought to be driven by at least two kinds of genes, oncogenes and tumor suppressor genes. Oncogenes are positive regulators of tumorgenesis, while tumor suppressor genes are negative regulators of tumorgenesis (Marshall, Cell 64:313-326, 1991; Weinberg, Science 254:1138-1146, 1991). Therefore, one mechanism of activating unregulated growth is to increase the number of genes coding for oncogene proteins or to increase the level of expression of these oncogenes (e.g., in response to cellular or environmental changes), and another mechanism is to lose genetic material or to decrease the level of expression of genes that code for tumor suppressors. This model is supported by the losses and gains of genetic material associated with glioma progression (Mikkelson, et al., J. Cellular Biochem. 46:3-8, 1991). Thus, changes in the expression (transcription) levels of particular genes (e.g., oncogenes or tumor suppressors) serve as signposts for the presence and progression of various cancers.